NBC Sports' Bob Costas speaks out in this exclusive interview with Lawrence O'Donnell about his Sunday night comments on the gun culture of America and the murder-suicide committed by Kansas City Chiefs linebacker Jovan Belcher.

By Kari Huus and Isolde Raftery, NBC News

NBC Sports commentator Bob Costas on Tuesday expanded on comments he made Sunday about the need for gun control in the wake of the murder-suicide of an NFL player.

"What I was talking about here – and I’m sorry if that wasn’t clear to everybody – was a gun culture," Costas said on MSNBC’s “Last Word with Lawrence O’Donnell,” referring to comments he made during his weekly half-time slot on NBC's Sunday Night Football. "I never mentioned the Second Amendment. I never used the words gun control. People inferred that. Now, do I believe that we need more comprehensive and sensible gun control? Yes I do. That doesn’t mean repeal the Second Amendment."

Belcher, a Kansas City Chiefs linebacker, shot and killed his 22-year-old girlfriend Kasandra Perkins on Saturday, before fatally shooting himself. The gun he used was registered legally, police confirmed on Monday.

Following Costas's comments, social media sites lit up as people sided with Costas or berated him.

In his interview with O'Donnell, Costas emphasized a gun culture "that demonstrates itself in different ways":

"It demonstrates itself in the Wild West, Dirty Harry mentality of people who actually believe that if a number of people were armed in the theater in Aurora, they would have been able to take down this nut-job in body armor and military-style artillery," he said. "It plays itself out in the inner cities where teenage kids are somehow armed to the hilt. And it plays itself in the sports world where young athletes are disproportionately armed."

Costas relayed an anecdote relayed to him by Tony Dungy, former head coach of the Indianapolis Colts. Dungy asked 80 football players at training camp if they owned a gun. Sixty-five hands went up.

"Even if all those guns were obtained legally, you can’t have 65 guys in their 20s – aggressive young men subject to impulses, without something bad happening," Costas said.

He continued: "Give me one example of an athlete – I know it’s happened in society – give me one example of an athlete by virtue of his having a gun, took a dangerous situation and turned it around for the better. I can’t think of a single one. Sadly, I can think of dozens that by virtue of having a gun, a professional athlete wound up in a tragic situation."

Responding to criticism that Costas didn't blame Belcher for the murder of his girlfriend: "No one is saying that Belcher is not responsible. However, the ready easy availability of guns makes mayhem easier. The easy availability of guns makes this sort of thing far more likely to occur."

Meanwhile Fox's Whitlock told Roland Martin of Roland Martin Reports that he hadn't gone far enough in his original commentary. He said that he took advantage of writing about gun violence in his column because so many people ignore the real world but they do pay attention to sports.

"I believe the NRA is the new KKK," Whitlock said. "And that the arming of so many black youths, and loading up our community with drugs, and then just having an open shooting gallery, is the work of people that obviously don’t have our best interests."